Manganese dioxide

Repeated dose toxicity: inhalation

Administrative data

Endpoint:

repeated dose toxicity: inhalation, other

Remarks:

other: two-generation study

Type of information:

experimental study

Adequacy of study:

supporting study

Study period:

2 July 2012 to 4 March 2013

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: see 'Remark'

Remarks:

A two-generation reproduction inhalation toxicity study conducted under GLP conditions and in accordance with a standardised guideline. Since animals were dosed over two generations, for a period of approximately 17 weeks, findings are considered to be indicative of repeated dose toxicity via the inhalation route. Since the study was conducted with manganese chloride, which represents a more available form of manganese, rather than with the registered substance itself, the study was assigned a reliability score of 2. Use of data on manganese dichloride is considered to be suitable and more precautionary since manganese dichloride is highly soluble; findings from the study are therefore considered to represent a worst case scenario for inorganic Mn compounds.

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2017

Report date:

2017

Materials and methods

Test guideline

Test guideline 1

Qualifier:

according to guideline

Guideline:

other: OECD Guideline 416 (Two-Generation Reproduction Toxicity Study)

Deviations:

no

Test guideline 2

Qualifier:

according to guideline

Guideline:

other: EPA OPPTS 870.3800 (Reproduction and Fertility Effects)

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Limit test:

no

Test material

Test material information

Constituent 1

Reference substance name:

manganese chloride

IUPAC Name:

manganese chloride

Test material form:

solid: particulate/powder

Details on test material:

- Name of test material (as cited in study report): manganese dichloride
- Molecular formula (if other than submission substance): MnCl2
- Physical state: solid
- Appearance: pink powder
- Storage condition of test material: ambient / dark / under inert gas

Test animals

Species:

rat

Strain:

Sprague-Dawley

Sex:

male/female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Age at study initiation: (F0) 6 - 8 weeks
- Weight at study initiation: (F0) Males: 155 - 298 g; Females: 130 - 194 g
- Housing: Animals were initially housed 2 per cage by sex in polycarbonate cages measuring approximately 61 x 43.5 x 24 cm with stainless steel grid tops and solid bottoms. A few days prior to mating, males were transferred to individual cages with a stainless steel grid insert measuring approximately 48 x 37.5 x 25 cm. After mating, the males were rehoused with their original cage-mates in solid bottomed cages. Mated females were transferred to individual solid bottomed cages (approximately 58.6 x 42.5 x 21 cm). White paper tissues were supplied as nesting material from Day 20 of gestation. Females with litters were retained in this cage type until termination after weaning. F1 animals retained after weaning were housed 2 per cage in cages measuring approximately 61 x 43.5 x 24 cm, as described above. The F1 animals then followed the same caging regime as described for the F0 animals.
- Diet: ad libitum
- Water: ad libitum
- Acclimation period: F0 animals were acclimatised for 13 days before the commencement of dosing. For at least 7 days prior to commencement of dosing the animals were conditioned to the restraint procedures used for nose-only exposure by placing the animals in the restraint tubes for gradually increasing period of restraint time up to the maximum expected duration to be used on the study.

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 17 - 26°C
- Humidity (%): 33 - 69%
- Air changes (per hr): at least 10 air changes per hour
- Photoperiod (hrs dark / hrs light): 12 hours light / 12 hours dark

Administration / exposure

Route of administration:

inhalation: aerosol

Type of inhalation exposure:

nose only

Vehicle:

air

Remarks on MMAD:

MMAD / GSD: See 'Exposure Conditions' under "Any other information on materials and methods incl. tables" for information.

Details on inhalation exposure:

GENERATION OF TEST ATMOSPHERE / CHAMBER DESCRIPTION
Test aerosols were generated using a Wright Dust Feed generator device. Exposure of the animals to the test material, or vehicle, was achieved utilising a modular nose only stainless steel flow past inhalation chamber.

- Dose formulation Preparation and analysis
Test material formulation was passed through a centrifugal grinder using the finest mesh available and then sieved using a mesh size of 100 μm prior to use, except on one occasion where a sieve mesh of 180 μm was used.

- Preliminary Aerosol Characterisation Investigations
Characterisation of the aerosol generating/exposure system was undertaken prior to commencement of the animal exposures to demonstrate satisfactory performance. Preliminary aerosol characterisation investigations demonstrated that aerosol concentrations were stable spatially within the exposure system and over time and that the particle size distribution investigations showed that test formulation particles for Groups 2 to 4 were respirable for the rat.

- Aerosol Generation
Test material aerosols were generated using a Wright Dust Feed generator device (Wright Dust Feed Mark II, BGI Industries, USA). Prior to the commencement of aerosol generation, a reservoir canister was packed with the test material powder formulation. The powdercake was slowly advanced into the scraper blade at an appropriate speed and scraped powder carried in a pressurised air stream.
The Wright Dust Feed generator device was operated at an appropriate target scraper speed, and air flow rate identified during the preliminary aerosol characterisation investigations. The generated test aerosols were then delivered to the flow past exposure chamber via a connecting tube manifold and mixed with dilution air to achieve the target aerosol concentration. A vacuum pump system was used to continuously exhaust test aerosols from the exposure chamber. Each aerosol generation system was operated to sustain a dynamic airflow sufficient to ensure an evenly distributed exposure aerosol.

- Inhalation Exposure (see Figure 1)
Exposure to the test aerosols was performed using appropriately sized modular nose only stainless steel flow past exposure chamber. Separate inhalation exposure systems were used for the delivery of test aerosol to each treatment group. Each inhalation exposure system was located in an extract booth (to prevent cross-group contamination). This exposure technique allowed a continuous supply of test aerosol to be delivered to each animal; the biased flow created using the flow-past chamber design ensured that there was no re-breathing of the test atmosphere.
For all inhalation exposures, the rats were restrained in clear, tapered, polycarbonate tubes with an adjustable back-stop to prevent the animals from turning in the tubes. The animals’ noses protruded through the anterior end of the restraint tubes which were connected to the exposure chamber by way of a push fit through rubber ‘o’ rings in the chamber wall. This exposure technique was used to minimise concurrent exposure by the oral and dermal routes. The exposure system was operated at an appropriate target total airflow. All flow rates (delivered and extracted) were monitored visually using calibrated flow meters. Exposure chamber flow rates, temperature and relative humidity were monitored and recorded at appropriate intervals during each daily exposure period.


TEST ATMOSPHERE
The aerosol concentration of test material formulation (Groups 2 to 4) or air (Group 1) in the animals’ breathing zone was measured gravimetrically for all groups at regular intervals throughout each daily exposure period.
The test aerosols were sampled using glass-fibre filters (47 mm Whatman GF/B) contained in a stainless steel filter holder in-line with a sampling system comprising a vacuum pump, flow meter and gas meter. Filter samples were collected from a reference sampling port representative of the animal exposure ports and test aerosol sampled for an appropriate duration and target flow rate to ensure that there was no overloading of the filter which would cause a reduction in sampling flow rate. The filters were weighed before and after sampling and the aerosol concentration calculated using the weight of formulation collected and the volume of air sampled.
In addition to the aerosol chamber concentration assessment, blank filter samples were taken to assess background levels of test material and retained for analysis.
All retained filters from Groups 1 to 4 were placed in amber glass jars and stored in a refrigerator set to maintain 4°C prior to analysis for the determination of the aerosol concentration of test material.
A real time aerosol monitor (Casella Microdust, Casella Measurements, UK) was used to assist in monitoring/ assessing the target concentrations at the start of generation each day and provided a continuous overview of any fluctuations in aerosol concentration.

PARTICLE SIZE DISTRIBUTION
The particle size distribution (PSD) of the test aerosols for Groups 2 to 4 was assessed using a Marple 296 Cascade Impactor. Measurements were undertaken at least once weekly up to Week 8 then at least every 4 weeks thereafter from all groups over the course of the dosing phase of the study. Particle size distribution samples were collected from a reference sampling port representative of the animal exposure ports and test aerosol sampled for an appropriate duration and target flow rate.
The particle size distribution of the test aerosols was determined from the plot of the cumulative percentage (by mass) of particles smaller than the cut-point of each impactor stage against the logarithm of each stage cut-point. The mass median aerodynamic diameter (MMAD) and geometric standard deviation (GSD) of the test aerosols were derived by Probit analysis using a computerised linear regression program.

Analytical verification of doses or concentrations:

yes

Details on analytical verification of doses or concentrations:

The gravimetric filters and particle size distribution samples collected and retained were subjected to chemical analysis using a method validated at Charles River, Edinburgh under Study No. 428133 (Method No. 2813). Full details of the analytical methodology are contained within that report.

Duration of treatment / exposure:

F0 animals were dosed for 10 weeks prior to mating, and then throughout mating, gestation and lactation until termination after the F1 generation had reached Day 21 of lactation. For F0 males, this treatment continued until the day prior to termination (a total of ca 17 weeks).
From the F1 generation, a group of animals were retained for post weaning assessments. These animals continued on study and were dosed for approximately 11 weeks after weaning, and then throughout mating, gestation and lactation until termination after the F2 generation had reached Day 21 of lactation. For F1 males, this treatment continued until the day prior to termination (a total of ca 17 weeks).

Frequency of treatment:

Daily (ca 6 hours per day, 7 days a week)
Females were dosed throughout gestation up to and including Day 19 of gestation. The animals were not dosed from Day 20/21 of lactation until their litters were born and then exposure was initially reduced to allow the dams to acclimatise to being away from their litter. The females were then dosed as follows:
From Day 1-2 of lactation: ca 1 hour per day
From Day 3-4 of lactation: ca 2 hours per day
From Days 5-20 of lactation until prior to termination (ca Day 21 of lactation): ca 6 hours per day.
Animals that did not litter down, re-commenced/continued dosing until the scheduled termination. Animals that had a litter loss continued on a 6 hour dosing regimen until scheduled sacrifice.

Doses / concentrations

Doses / concentrations 1

Remarks:

Doses / Concentrations:
0, 5, 10, 20 µg/L
Basis:
nominal conc.

Doses / concentrations 2

Remarks:

Doses / Concentrations:
0, 6, 15, 25 µg/L
Basis:
other: analytical conc. (F0 generation)

Doses / concentrations 3

Remarks:

Doses / Concentrations:
0, 4, 10, 17 µg/L
Basis:
other: analytical conc. (F1 generation)

No. of animals per sex per dose:

- F0 Generation
28 males and 28 females per dose

- F1 Generation
26 animals per sex were dosed at the target concentration of 0 µg/L
24 animals per sex were dosed at the target concentration of 5 µg/L
24 animals per sex were dosed at the target concentration of 10 µg/L
25 animals per sex were dosed at the target concentration of 20 µg/L

Control animals:

yes, concurrent vehicle

Details on study design:

- Selection and Weaning of F1 Animals
From each group, at least 24 males and 24 females were selected for post-weaning assessments. The selected pup(s) were the median’th weight pup(s) of that sex in the litter on Day 21 of lactation. These pups were removed from their mother on Day 21 of lactation, individually identified and housed in a new cage. Pups that were not selected for post-weaning assessments remained with their mother until sacrifice.

Examinations

Observations and examinations performed and frequency:

CAGE SIDE OBSERVATIONS: Yes
- All animals were checked for early each morning and as late as possible each day for viability. Furthermore, all animals were examined for reaction to treatment daily during the course of dosing on the study. The onset, intensity and duration of any signs were recorded.

DETAILED CLINICAL OBSERVATIONS: Yes
- Time schedule: Once each week starting in pretrial, all animals received a detailed clinical examination, including appearance, movement and behaviour patterns, skin and hair condition, eyes and mucous membranes, respiration and excreta.

BODY WEIGHT: Yes
- Time schedule for examinations: Weights of F0 animals were recorded one week prior to the first day dosing, then weekly thereafter until the start of the mating period. Males continued to be weighed weekly until termination; but for females, weighing resumed on Day 0 of gestation (the day of detection of
a positive mating sign), and then on Days 7, 14 and 20 of gestation and Days 1, 7, 14 and 21 of lactation (where the day of birth of the litter was designated Day 0 of lactation).
Post-weaning F1 animals were weighed weekly, starting on a suitable day within one week of weaning of the majority of the litters and continued until termination for males and until mating commenced for females. Mated F1 females were weighed on Days 0, 7, 14 and 20 of gestation, then on Days 1, 7, 14 and 21 of lactation. Females that did not show a positive mating sign were weighed weekly until parturition or termination. Females who had a positive mating sign but failed to litter reverted to the weekly weighing regimen following their theoretical Day 24 of gestation.

FOOD CONSUMPTION: Yes
- Time schedule: Food consumption was quantitatively measured for both sexes weekly, starting one week before treatment commenced (F0 animals) or from a suitable day within one week of weaning of the majority of animals (F1 animals) until placement of males in individual cages prior to mating. Weekly measurements continued after the 14 day mating period. For females, following a clear indication of mating, food consumption was measured over Days 0-7, 7-14 and 14-20 of gestation and Days 0-7, 7-14 and 14-21 of lactation

WATER CONSUMPTION: Yes
- Monitoring of water consumption was limited to a visual inspection of the water bottles on a regular basis throughout the study.

OTHERS (REPROTOXICITY):
- Observation of females with litters during lactation, seuxal maturation, estrous cyclicity, sperm parameters, litter observations.

Sacrifice and pathology:

> PARENTAL ANIMALS
SACRIFICE
Termination for the adult females was at or shortly after weaning of their litters (Day 21 of lactation). Termination for males was around the time of the termination of the females.
Animals 10 days of age or more were killed by exposure to carbon dioxide followed by exsanguination.

UNSCHEDULED DEATHS
These animals, including those killed or found dead, had a terminal body weight recorded and were necropsied with a view to diagnosis of the cause of the animal’s condition or cause of death. An external examination was followed by inspection of the cranial, thoracic and abdominal contents. The tissues list for animals at scheduled necropsy along with representative samples of abnormal tissues, together with any other tissues considered appropriate, were fixed in neutral 10% formalin. The reproductive tracts of all females were also examined.

GROSS NECROPSY
Animals were subjected to a complete necropsy examination, which included evaluation of external surfaces and orifices; cranial; thoracic, abdominal, and pelvic cavities with their associated organs and tissues. Necropsy examinations consisted of an external and internal examination and recording of observations for all animals.

ORGAN WEIGHTS
The following were weighed: brain, epididymides, adrenal glands, pituitary gland, prostate glang, thyroid glands, kidneys, liver, lung, ovaries, spleen, testes, uterus.

HISTOPATHOLOGY
Histological examination was conducted on all adults in the Control and High dose groups of the F0 and F1 generation and a selection of the premature decedents. After a review of the data, histological examination of the respiratory tract tissues of the Control and High dose animals, it was considered appropriate to conduct histopathology on the respiratory tract of all adult animals of the F0 and F1 generation.
The following tissues were processed for microscopic evaluation: adrenal glands, larynx, left testis, left epididymis, lung, bronchial lymph node, cervical lymph node, nasal cavity, ovaries, pharynx, prostate, pituitary gland, seminal vesicles and coagulating glands, trachea (anterior and posterior), uterus (with oviducts and cervix), vagina.
Additionally, a Periodic Acid Schiff and Haematoxylin (PAS-H) stained section was prepared from the left testis.
A detailed qualitative examination of the testes was made, taking into account the tubular stages of the spermatogenic cycle. The examination was conducted in order to identify treatment-related effects such as missing germ cell layers or types, retained spermatids, multinucleate or apoptotic germ cells and sloughing of spermatogenic cells into the lumen. Any cell- or stage-specificity of testicular findings were noted.
The examination of the ovaries included quantification of the primordial and growing oocytes, and the confirmation of the presence or absence of the corpora lutea.

Other examinations:

SACRIFICE / GROSS NECROPSY (OFFSPRING)
Pups that were not selected for post-weaning assessments were killed at the same time as their mother. Animals less than 10 days of age were killed by intra-peritoneal injection of sodium pentobarbitone.

Pups that died prematurely were sexed and checked for external abnormalities. Any abnormal pups were, where practicable, fixed in 10% formalin or methylated ethyl alcohol, as appropriate, for optional further examination.
At planned termination of offspring, 3 male and 3 female pups were necropsied and examined for external abnormalities followed by macroscopic examination of the tissues and organs of the cranial, thoracic and abdominal cavities in situ. Samples of any grossly abnormal tissues were preserved and the weights of the brain, spleen and thymus were recorded from one of the 3 pups of each sex; these organs were preserved. Representative samples of any abnormal tissues from any of the 6 pups were also preserved.
The following were weighed for all animals: brain, epididymides, adrenal glands, pituitary gland, prostate glang, thyroid glands, kidneys, liver, lung, ovaries, spleen, testes, uterus.
Histological examination was conducted on the brain, spleen and thymus of Control and High dose F1 and F2 weanlings (the selected weanlings at necropsy). A single H&E section was cut, stained and evaluated.

Statistics:

Unless otherwise stated, all statistical tests were two-sided and performed at the 5% significance level using in house software. Pairwise comparisons were only performed against the control group.
Select body weight and food consumption were analysed for homogeneity of variance using the ‘F-Max’ test. If the group variance appeared homogeneous, a parametric ANOVA was used and pairwise comparisons were made using Fisher’s F-protected LSD method via Student’s t-test ie pairwise comparisons was made only if the overall F-test was significant. If the variances were heterogeneous, log or square root transformations were used in an attempt to stabilize the variances. If the variances remained heterogeneous, then a Kruskal-Wallis non-parametric ANOVA was used and pairwise comparisons were made using chi squared protection (Via z tests, the non-parametric equivalent of Student’s t test).
Organ weight data was analysed as above, and by analysis of covariance (ANCOVA) using terminal body weight as the covariate.

Results and discussion

Results of examinations

Clinical signs:

effects observed, treatment-related

Mortality:

mortality observed, treatment-related

Body weight and weight changes:

effects observed, treatment-related

Food consumption and compound intake (if feeding study):

effects observed, treatment-related

Food efficiency:

not examined

Water consumption and compound intake (if drinking water study):

not examined

Ophthalmological findings:

not examined

Haematological findings:

not examined

Clinical biochemistry findings:

not examined

Urinalysis findings:

not examined

Behaviour (functional findings):

not examined

Organ weight findings including organ / body weight ratios:

effects observed, treatment-related

Gross pathological findings:

no effects observed

Histopathological findings: non-neoplastic:

effects observed, treatment-related

Histopathological findings: neoplastic:

no effects observed

Details on results:

MORTALITY (PARENTAL ANIMALS)
- F0 animals
Animal 138 (Group 1F) was killed prematurely on Day 97 of the study. The animal was sacrificed at the time of parturition as the animal had difficulty giving birth and there was a pup protruding from the vagina. Animal 330 (Group 3F) was killed prematurely on Day 94 of the study. The animal had a prolonged parturition. There were no abnormalities detected at histological evaluation.
Animals 228 (Group 2M) and 236 (Group 2F) were killed prematurely on Day 85 and Day 83, respectively due to clinical signs. The male animal had shavings stained red, a cold body, reduced activity, rolling gait, staggering and weight loss. Necropsy findings for this animal included yellow froth filled duodenum, ileum and jejenum, pale foci on kidney, pale foci left lung lobe, enlargement of adrenal gland, small thymus, urinary bladder adhesions. Histological findings included a mild ulcer in the larynx. The female had partially closed eyes, dilated pupils, tremors, unkempt coat, walking on tip toes, irregular respiration, staggering and subdued. Necropsy findings included pale extremities and fluid accumulation in both horns of the uterus (the animal was sacrificed prior to having a clear indication of mating). There were no abnormalities detected at histological evaluation.
There was no treatment related pattern to these deaths and these were not positively attributed to treatment.
- F1 animals
Animal 521 (Group 1M), animal 717 (Group 3M), animal 748 (Group 3F), Animal 751 (Group 3F) and animal 816 (Group 4M) were killed prematurely. However, none of these premature deaths were considered to be related to treatment but were considered to be due to accidental injury.

CLINICAL SIGNS (PARENTAL ANIMALS)
- F0 animals
At target 20 μg/L, there were 2/28 males noted as having wheezing respiration. Animal 333 (Group 3F) had clinical signs including wheezing, unkempt coat, walking on tip toes, rolling gait and weight loss recorded over ca Days 83-90 of the study. Due to the signs dosing for the animal was stopped for a few days. However, the animal recovered from these signs and dosing continued until scheduled termination. As no similar findings were noted in the other animals, these signs were considered to be incidental. Other clinical signs noted in the F0 animals were considered to be incidental or due to the dosing procedure (wet, unkempt coat).
- F1 animals
Clinical observations noted in the F1 animals were considered to be incidental or due to the dosing procedure (wet, unkempt coat).

BODY WEIGHT (PARENTAL ANIMALS)
- F0 animals
At target 20 μg/L, there was a decrease in body weight gain in males over Days 0-21 of the study. From Day 21 of the study, the body weight gains were generally comparable to the controls but the group mean weights remained lower than the controls throughout the study. At target 20 μg/L, there was a group mean body weight gain in females prior to mating were similar to the controls, however body weight gains over Days 0-20 of gestation were slightly lower than the controls. Gains over lactation were similar to the controls.
- F1 animals
At target 20 μg/L, there was a reduction in group mean body weight gain of the males during the first 5 days of the study, however gains over the following week were greater than the controls and then remained comparable with the controls throughout the remainder of the treatment period. Slight intergroup differences in group mean body weight gains in the F1 females prior to mating were too small to be attributed to treatment. At 20 μg/L, there was a slight reduction in body weight gains throughout gestation compared to the controls.
There were no effects of treatment noted in the lactation females.

FOOD CONSUMPTION (PARENTAL ANIMALS)
- F0 animals
At target 20 μg/L, there was reduced food consumption for males throughout the majority of the study, compared with the controls. At target 20 μg/L, there was a transient reduction in food consumption in the females on commencement of treatment compared with the controls; however, consumption for the remainder of the pre-mating period was similar to the controls. Slight intergroup differences in the group mean food consumption in the males at target 5 μg/L and target 10 μg/L were not attributed to treatment. Slight intergroup differences in group mean food consumption throughout gestation and lactation were not attributed to treatment.
- F1 animals
At target 20 μg/L, there was a slight reduction in group mean food consumption in the males over Days 40-68 of the study; these reductions achieved statistical significance. Slight intergroup differences in group mean food consumption at target 5 μg/L and target 10 μg/L were not attributed to treatment. Group mean food consumption in the females prior to mating and throughout gestation and lactation were comparable to the controls.

ORGAN WEIGHTS (PARENTAL ANIMALS)
- F0 animals
At target 20 μg/L, reduced brain weights in males achieved statistical significance (P<0.05) compared with controls. However, the lower body weight was also statistically significant (P<0.05) following covariance analysis brain weight did not achieve significance and therefore was not positively attributed to treatment. In all treated females, there was a statistically significant increase in lung weights, compared with the controls; these increases were still present following covariance analysis (P<0.01 at target 5 μg/L and P<0.001 at target 10 and 20 μg/L). Other slight differences in organ weights such as an increased thyroid weight in males at target 5 μg/L and an increase in kidney weights of females at target 10 μg/L were not attributed
to treatment.
- F1 animals
At target 5 and 10 μg/L, kidney weights in males were statistically higher than the control, however there was no dose relationship to this increase and following covariance analysis, these findings were no longer evident. At target 10 and 20 μg/L, there was a statistically significant increase in kidney weights in females (P<0.05 at target 10 μg/L and P<0.001 at target 20 μg/L) following covariance analysis. Other slight differences in organ weights such as an increased adrenal weight in females at target 20 μg/L were not attributed to treatment.

GROSS PATHOLOGY (PARENTAL ANIMALS)
There were no treatment related gross findings recorded. The findings observed were considered incidental, of the nature commonly observed in this strain and age of rat, and/or were of similar incidence in control and treated animals and, therefore, were considered unrelated to administration ofthe test material.

HISTOPATHOLOGY (PARENTAL ANIMALS)
There were no treatment related findings observed in the reproductive tract in the F0 or F1 generations.
Histological findings were confined to the respiratory tract. Inhalation of the test material was associated with microscopic findings in the nasal cavity, larynx, lung and trachea (including carina) in all dose groups of the F0 generation, in the pharynx of F0 generation animals exposed to target 10 and 20 μg/L; in the nasal cavity, pharynx, larynx and lung in all dosed group of the F1 generation and in the trachea (including carina) of F1 generation animals exposed to target 10 and 20 μg/L.

OTHER FINDINGS (PARENTAL ANIMALS)
There were no treatment-related effects on estrous cyclicity, sperm parameters or on mating performance, fertility or duration of gestation in either generation.

Effect levels

Dose descriptor:

NOEL

Remarks:

F0 and F1

Effect level:

20 mg/m³ air

Based on:

test mat.

Sex:

male/female

Basis for effect level:

other: No treatment related effects were observed

Target system / organ toxicity

Critical effects observed:

not specified

Any other information on results incl. tables

Blood Analysis Results

F0 Males
Time-point	Blood Mn conc (ppb w/v (ng/mL))
	Group 1 (Control)	Group 2 (5 µg/L)	Group 3 (10 µg/L)	Group 4 (20 µg/L)
Pre-treatment	7	7	7	6
Prior to mating	6	13	23	27
Prior to Necropsy	6	19	27	29
F0 Females
Time-point	Blood Mn conc (ppb w/v (ng/mL))
	Group 1 (Control)	Group 2 (5 µg/L)	Group 3 (10 µg/L)	Group 4 (20 µg/L)
Pre-treatment	7	7	7	7
Prior to mating	6	16	28	39
Prior to Necropsy	7	16	24	33

At target 20 μg/L, manganese levels prior to mating were 350% higher than controls in males and 550% higher than controls in females at the pre-mating timepoint. At terminal necropsy, these values were 383% and 371% for males and females.

At target 10 μg/L, manganese levels prior to mating were 283% higher than controls in males and 367% higher than controls in females at the pre-mating timepoint. At terminal necropsy, these values were 350% and 243% for males and females.

At target 5 μg/L, manganese levels prior to mating were 117% higher than controls in males and 167% higher than controls in females at the pre-mating timepoint. At terminal necropsy, these values were 217% and 129% for males and females.

F1 Males
Time-point	Blood Mn conc (ppb w/v (ng/mL))
	Group 1 (Control)	Group 2 (5 µg/L)	Group 3 (10 µg/L)	Group 4 (20 µg/L)
Pre-treatment	12	16	16	17
Prior to mating	6	9	13	19
Prior to Necropsy	6	9	14	21
F1 Females
Time-point	Blood Mn conc (ppb w/v (ng/mL))
	Group 1 (Control)	Group 2 (5 µg/L)	Group 3 (10 µg/L)	Group 4 (20 µg/L)
Pre-treatment	13	12	15	15
Prior to mating	6	10	16	23
Prior to Necropsy	7	10	16	21

At target 20 μg/L, manganese levels prior to mating were 217% higher than controls in males and 283% higher than controls in females at the pre-mating timepoint. At terminal necropsy, these values were 250% and 200% for males and females.

At target 10 μg/L, manganese levels prior to mating were 112% higher than controls in males and 133% higher than controls in females at the pre-mating timepoint. At terminal necropsy, these values were 167% and 129% for males and females.

At target 5 μg/L, manganese levels prior to mating were 50% higher than controls in males and females at the pre-mating timepoint. At terminal necropsy, these values were 50% and 43% for males and females.

The manganese concentrations in the blood of all the treated F1 animals were lower than the same time-point levels of the F0 generation animals.

Applicant's summary and conclusion

Conclusions:

Under the conditions of the study the No Observed Effect Level (NOEL) of manganese chloride, was determined to be 20 µg/L, the highest concentration tested.

Executive summary:

The subchronic reproductive toxicity of manganese chloride was investigated in a two generation study which was conducted under GLP conditions and in accordance with the standardised guidelines OECD 416 and EPA OPPTS 870.3800.

F0 animals were randomised into 3 test groups and one control group, each containing 28 males and 28 females. These animals were dosed with manganese chrloride for 10 weeks prior to mating, and then throughout mating, gestation and lactation until termination after the F1 generation had reached Day 21 of lactation.

From each treatment group, at least 24 males and 24 females were retained for post weaning assessments. These animals continued on study and were dosed for approximately 11 weeks after weaning, and then throughout mating, gestation and lactation until termination after the F2 generation had reached Day 21 of lactation.

Animals were monitored for clinical signs of toxicity and for effects on body weight, food consumption, effects on oestrous cycles, mating performance, pregnancy performance, difficulty or prolongation of parturition, and for deficiencies in maternal care. The offspring were monitored for survival and growth up to weaning. In addition, the following endpoints were evaluated: gross necropsy findings, organ weights, histopathology evaluation, qualitative examination of testes and examination of the ovaries and sperm evaluation. Blood samples were taken from all adult animals for bioanalytical analysis prior to dosing, prior to mating and prior to weaning/necropsy.

Clinical signs of reaction to treatment to inhalation exposure of manganese chloride were confined to a few animals with wheezing respiration in the F0 generation exposed to target levels of 10 and 20 μg/L. At target 20 μg/L, overall body weights and food consumption of the F0 males throughout the study were lower than controls. In the F1 generation, the body weight gain of the males at target 20 μg/L were transiently reduced on commencement of treatment; in addition, the food consumption at this level was lower than the controls over Days 19-68 of treatment. At target 20 μg/L, there was a slight reduction in group mean body weight gains during gestation in both generations. Gains throughout lactation were similar to controls.

There was no effect of treatment on oestrous cycles, mating performance, fertility or duration of gestation or litter size in either generation. Slight intergroup differences in the pup survival were too small to be attributed to treatment. Group mean litter and pup weights in the F0 generation litters were comparable with controls. At target 20 μg/L, group mean litter weights were slightly lower than the controls, however this reflected a slightly smaller litter size at this level. The mean pup weights in both males and females were comparable to the controls and the slightly lower litter weights were not attributed to treatment. There were no effects of treatment on the sexual maturity of the F1 animals.

At target 10 and 20 μg/L, there was a statistically significant increase in kidney weights compared to the controls, however there was no alteration in the normal structure of these organs, as seen by microscopy (at target 20 μg/L). In all treated F0 females, there was a statistically significant increase in lung weights compared to the controls; this increase in lung weights was not evident in the F1 females.

Inhalation of manganese chloride was associated with microscopic findings in the nasal cavity, larynx, lung and trachea (including carina) in all dose groups of the F0 generation, in the pharynx of F0 generation animals exposed to target 10 and 20 μg/L; in the nasal cavity, pharynx, larynx and lung in all dosed group of the F1 generation and in the trachea (including carina) of F1 generation animals exposed to target 10 and 20 μg/L.No test substance-related findings were observed in the reproductive tract in the F0 or F1 generations and in tissues examined from weanlings in the F1 and F2 generations. However, these effects on the respiratory tract are specific to manganese chloride because it dissolves and recrystalises as sharp, irritating, crystals in the respiratory tract. This physico-chemical property of the chloride is not common to the carbonate and hence it can be concluded that the effects on the respiratory tract would not be apparent following exposure to manganese carbonate.

In all treated groups of the F0 generation, the levels of manganese in the blood increased significantly on commencement of dosing (as recorded prior to mating) in both males and females. The concentrations recorded prior to mating and prior to necropsy were comparable in all groups which did not indicate any obvious accumulation over the dosing period. In the F1 generation, pre-treatment concentrations in all groups were higher than the F0 generation pre-treatment values. In addition, at target 5 and 10 μg/L in the F1 generation, the pre-treatment values were generally higher or similar to the values recorded during the dosing period, indicating that the exposure to the test substance through the mother’s milk during lactation resulted in an increased exposure to the test substance in the F1 animals from birth. At target 20 μg/L, the concentrations of the F1 males and females throughout the dosing period were greater than the pre-treatment values indicating an increased exposure throughout the dosing period.

In conclusion, under the conditions of this study, the No Observed Effect Level was considered to be the target dose level 20 μg/L.